Tactics Trainer Chart Uses Incorrect Units

I love the tactics trainer and use it all the time (and love this site as well - great job!) but I feel that the tactics trainer rating chart uses the incorrect units. Currently it uses "days" or "date" on the x-axis and rating on the y-axis. But this means if I do 50 problems at the beginning of the month, one problem a day for the next month, and then 50 again at the end of the month, each day is treated with the same weight. And if I don't do any problems for 6 weeks the chart shows my rating as staying the same and distorts the chart.

Instead, I suggest using "Number of Problems Completed" on the x-axis. This would give each problem equal weight, adjust for days that I do many or no problems, and overall give a much more accurate chart. This is similar to how chess uses "moves" instead of minutes to measure the progress of a game.